<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="jquery.min.js"></script>
</head>
<body>
    <div>div</div>
    <div class="nav"></div>
<p>P</p>
<ol>
    <li>1</li>
    <li>1</li>
    <li>1</li>
    <li>1</li>
</ol>
<ul>
    <li>1</li>
    <li>1</li>
    <li>1</li>
    <li>1</li>
</ul>
<script>
    // jQuery选择器使用 各个选择器格式一致 和css使用差不多
    $(function() {
       console.log( $('.nav'));//类选择器
       console.log($('ul li'));//后代选择器
    })
   
</script>
</body>
</html>